Regulation of bta-miRNA29d-3p on lipid accumulation via GPAM in dairy cow mammary epithelial cells

MicroRNAs (miRNAs) are small RNA molecules of approximately 22 nucleotides that are involved in the regulation of various biological processes. Increasing evidence has identified that miR-29 is a key regulator of cholesterol and fatty acid synthesis. Mimics and inhibitors of bta-miRNA29d-3p were transiently transfected in dairy cow mammary epithelial cells (DCMECs) to reveal the regulation of bta-miRNA29d-3p on lipid accumulation in DCMECs. Results showed that overexpression of bta-miRNA29d-3p significantly inhibited the expression of genes related to triglyceride (TAG) synthesis, namely, <em>DGAT1</em> and mitochondrial glycerol-3-phosphate acyltransferase (<em>GPAM</em> , <em>P</em> &lt; 0.01) and down-regulated TAG levels in cells (<em>P</em> &lt; 0.05). The expression of fatty acid synthesis and desaturation-related genes <em>FASN</em>, <em>SCD1</em>, <em>ACACA</em>, and transcription factor <em>SREBF1</em> also decreased. Interference of bta-miRNA29d-3p significantly increased the expression of <em>GPAM</em>, <em>DGAT1</em>, <em>FASN</em>, <em>SCD1</em>, <em>ACACA</em>, and <em>SREBF1</em> (<em>P</em> &lt; 0.01), and significantly upregulated the concentration of TAG in cells. Furthermore, luciferase reporter assay confirmed that <em>GPAM</em> is a direct target of bta-miRNA29d-3p. In summary, bta-miRNA29d-3p modulates fatty acid metabolism and TAG synthesis by regulating genes related to lipid metabolism in DCMECs and targeting <em>GPAM</em>. Thus, bta-miRNA29d-3p plays an important role in controlling mammary lipid synthesis in cows.